The new ladder rating system should have a chronological sorting so that the bloc of 20 unexpired games that started last and don't have any unfinished games in-between are considered for rating and rank.
Expiration time could still be 3 months, or even less, to avoid rating stagnation.
An opponent going on vacation / intentionally stalling was the only problem I saw last time chronological rating was discussed. You could make an exception for such cases, such as this:
If the opponent has used more than twice as much time for his moves compared to you over the course of the entire game, and at least 5 turns have passed, then it is assumed that he is stalling and this game will be skipped for your rating. It will be considered again when the game has finished.
Maybe better to put an actual time limit on that instead of twice as much time. Otherwise the new way to game the rating system would be to make 5-6 very fast turns so the game will be skipped for your rating.
players taking 2 days on average per turn and with atleast 5-6 turns passed would be a better criteria.
